Volcanoes

What are the 3 major types of volcanoes?

• Shield– Gentle sloping sides, slow moving/runny lava

• Composite– Tall, steep sides. Very violent eruptions. Thick

sticky lava. Layers made of __________, _____, and pyroclastic materials

• Cinder Cone– Short, ______ sides. Layers made of ash.– What do you think pyroclastic means?

LAVA DOME

A type of volcano often formed on or near another active volcano. Magma rises just under the crust and cools.

What is volcanism?

Any activity that includes the movement of _________ toward or onto the ________ of the earth.

Because of high temperature and pressure in the earth- pockets of magma form when surrounding rock ______, as more rock melts, the pocket grows

Predict what happens next.

Why does the magma come to the surface?

The magma is hotter, and less _______ than rock so it rises to the surface through _______ in the rocks- melting more rock.

This occurs mostly at plate boundaries

Any magma that makes it to the surface is called ______- the opening it comes through is called a ______.

The build up of material over the vent is a _______.

http://www.youtube.com/watch?v=mYekQtFLT2Ahttp://www.youtube.com/watch?v=ZZnvzSpNLAE&feature=related

What state do you think has the most volcanoes?

Volcanoes at subduction zones

What happens here? Draw a picture of what you think happens.

O-C plate boundaries:Oceanic is pushed under the continental, melting the plate. Magma rises to the surface _________, the crust buckles _______, trenches form at the boundary.

O-OSame as O-C, just under water. Volcanoes here are called island ______volcanoes. Japan and Alaska

Why does Oceanic plate subduct more often the cont?

Volcanoes at subduction zones

What happens at divergent boundaries?

As plates move apart magma comes to the surface making mid ocean _________

Most of the eruptions here goes unnoticed, mountains and volcanoes are continuously forming. They can be seen only on land in ___________.

Iceland is in part a __________.

Where is Iceland?

What happens at divergent boundaries?

Hot Spots

Not all volcanoes are on __________.Sometimes magma can rise to the surface in

the _____________ of a plate.These volcanoes seem like they are

stationary, however, as the plate moves over the hotspot new volcanoes are formed, and old ones are __________ away.

http://www.youtube.com/watch?v=tfXGbzgGJ74&feature=related

Types of lavaDifferent types of ____________ make different

types of lava.

Mafic- oceanic crust- full of ________ and magnesium- dark in color- small __________- quiet eruptions

Felsic- continental crust- ________rich- light in color- large crystals-violent eruptions

Pahoehoe (Pah-Hoy-Hoy)- slow moving- “______”

Aa (Ah Ah)- quick cooling- jagged chunks

Pillow lava- when lava flows onto the ocean floor through ____________

Write 2 things you learned about volcanoes today.